Solve for $n$ : $20 + n = 27$
Explanation: Subtract $20$ from both sides: $ \begin{eqnarray} \\ 20 + n &=& 27 \\ \\ {-20} && {-20} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{20 + n} &\hphantom{=}& \hphantom{27} \\ n &=& 27 {- 20} \\ \end{eqnarray} $ Simplify. $ n = 7$